1. Field of the Invention
The present invention relates to an optical storage device, or more particularly, to an optical storage device in which electrical means are substituted for the capabilities of sensors that cannot be stowed in the optical storage device when the optical storage device is made thinner.
2. Description of the Related Art
Speaking of existing storage media, a compact cassette for recording sound which utilizes magnetic tape, a video cassette for recording pictures, and the like, are known. However, data recorded on any of these media is not accessible at random. Besides, the recorded data is analog information. There are therefore such drawbacks that reproduced data may contain noise, that the data may be deteriorated when copied, that the data may be deteriorated when stored for a prolonged period of time, and the like.
As for another kind of storage medium, an optical disk making it possible to record a digital signal, into which data is converted, in a data track on a disk, and to read the signal using returned light of a laser beam irradiated to the data track has been put to practical use. Examples typical of the optical disk are a compact disk (CD) for recording music, a laser disk (LD) for recording pictures, and the like. Moreover, development of a digital video disk (DVD) that is compactly designed for recording pictures is in progress. On the other hand, since these kinds of optical disks have large storage capacities, they have come to be used as data storage media by the names of a CD-ROM, LD-ROM, and the like.
In recent years, a magneto-optical disk making it possible to record data on a recording medium using a laser beam and magnetism, and to read the data using the laser beam has also been put to practical use. Since this kind of magneto-optical disk has a large storage capacity, it is used as an optical storage device in the form of an external memory for a computer.
As mentioned above, storage media using light include an optical disk and a magneto-optical disk. Herein, a description will proceed on the assumption that the storage media using light are regarded generally as optical disks.
The optical disk used for an optical storage device is coming into the spotlight as a storage medium having a pivotal stance in the multimedia systems that have appeared in recent years, and is normally stowed in a cartridge to ensure portability. The optical disk cartridge is loaded in an optical disk unit. Information is then written to or read from the optical disk by means of an optical head.
Currently, the optical disk unit often used externally connected to a computer via an SCSI interface.
Recently, it has become desirable to mount an optical disk unit in a portable personal computer. Technological development is under way at a quick pace in an effort to realize a more compact and lightweight design. Taking, for instance, a floppy disk unit and hard disk unit which have been used as an external storage for a personal computer in the past, the trend toward a more compact design has progressed so greatly that a floppy disk unit or a hard disk unit can be mounted in a slot in a main unit of a personal computer which is approximately 17 mm thick.
For inserting the optical disk unit that is an optical storage device into the slot of approximately 17 mm thick and designed for a floppy disk unit or hard disk unit, the existing optical disk unit must be made thinner.
However, when the optical disk unit is made thinner so that it can be inserted into the slot of approximately 17 mm thick designed for a floppy disk unit or hard disk unit and formed on a personal computer, since a space inside the optical disk unit is restricted vertically, a conventional position sensor and a sensor for detecting the position of an objective lens must be made smaller. Because the size of position sensor and the sensor for detecting the position of an objective lens make it hard to position a carriage having an optical head mounted thereon inside the optical disk unit.